Avr OS on Arduino

What about an OS to run on your Arduino? Ok not in the way big os, remember Arduino has limited performance, but some of the basics, like spinlocks/multitask can be integrated with the AVR Os. As you know Arduino uses an AVR Compilant Processor, so its easy to port the code. The user [chris] sent us the way to do it, with also a simple sketch to print the classic “Hello World”.